A liquid crystal display device is one of display devices and has advantages of lightness, thinness, low cost, low power consumption, an excellent junction with an integrated circuit, and the like, and thus is widely applied for a laptop, a monitor, and a TV screen. The liquid crystal display device includes a lower substrate including a black matrix, a color filter, and an indium tin oxide (ITO) pixel electrode, and an upper substrate including an active circuit portion including a liquid crystal layer, a thin film transistor, an electricity storage capacitor layer, and an ITO pixel electrode. In the liquid crystal display device, color filters are formed in a pixel region by sequentially laminating a plurality of color filters (in general, formed of three primary colors such as red (R), green (G), and blue (B)) in a predetermined order to form each pixel, and a black matrix layer is disposed in a predetermined pattern on a transparent substrate to form a boundary between the pixels.
A color filter may be fabricated in a pigment dispersion method. According to the pigment dispersion method, a coloring thin film is formed by repeatedly coating a photopolymerizable composition including a colorant on a transparent substrate provided with a black matrix, exposing a desired pattern to a light, removing an unexposed part with a solvent, and thermally curing the resulting product. The photosensitive resin composition for a color filter used in the pigment dispersion method generally includes an alkali soluble resin, a photopolymerizable monomer, a photopolymerization initiator, an epoxy resin, a solvent, other additives, and the like. The pigment dispersion method has been actively applied to an LCD of a mobile phone, a laptop, a monitor, TV, and the like. However, a photosensitive resin composition for a color filter for the pigment dispersion method has recently required more improved performance as well as excellent pattern characteristics. Particularly, high luminance and high contrast ratio along with high color reproducibility are required.
An image sensor is a part for photographing images in a portable phone camera or a DSC (digital still camera). It can be classified as a charge-coupled device (CCD) image sensor and a complementary metal oxide semiconductor (CMOS) image sensor depending upon the manufacturing process and the application method. A color imaging device for a charge-coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor includes color filters each having filter segments of mixing primary color of red, green, and blue, and the colors are separated. A recent color filter mounted in the color imaging device has a pattern size of 2 μm or less, which is 1/100th to 1/200th of the pattern size of a conventional color filter pattern for LCDs. Accordingly, increased resolution and decreased pattern residues are important factors for determining the performance of a device.
A color filter fabricated by using a conventional pigment-type photosensitive resin composition has a limit in luminance and a contrast ratio due to the size of pigment particles. In addition, a color imaging device for an image sensor needs a smaller dispersion particle diameter for forming a fine pattern.